This invention relates to systems and methods for precisely detecting the presence of explosives, non-military homemade explosives (HME) and explosives residue at trace or bulk levels. The new system and method may provide a compact test unit that incorporates a test method that may allow testing of sample articles at a selected location. The detection method may provide a sequence of detection over a combination of applied heat profiles, time profiles, and sequence of reagents. The detection unit may use chemicals and other elements that reduce the hazard to a user.
Chemical detection of the presence of explosives and explosive residue has been known for many years. The methods and chemicals used in the past have tended to be cumbersome to transport and put into use at a selected site or location and the testing may have been time consuming. Special testing devices and apparatus may have been developed for specific explosives, but they may have been unreliable, limited to only a few classes of different explosive types, dangerous to the user due to the chemicals used, not reproducible at low level detection, or otherwise limited in capability of identifying an explosives contaminated site or object.
A previously used chemical explosives identification technique that may have been reasonably reliable is thin layer chromatography or TLC. Testing apparatus and methods have been developed including kits for on-site testing. The colorimetric devices and methods including those using a TLC plate may have shortcomings for effective, efficient testing, e.g., difficulty of use, length of time, solvent waste disposal, use of toxic chemicals, large work area, need for calibration, limited type or number of explosive compounds detectable, use of glass as well as other issues.
The use of colorimetric testing or spot tests may have been recognized for many years as chemical reagents and methods were identified to detect the presence of a particular explosive. The colorimetric tests may afford quick results, may be easy to perform and may be sensitive relative to the explosive sample content, but may be limited in the number of different explosives detected. The most common spot test method may be to have explosives react with a base, then allow time or heat the sample, then perform a Griess reaction test, and then allow more time or heat the sample. Various formulations of the Griess reagent may have been developed. Also numerous types of substrates, sorbent materials or swipes, such as, wool, cotton, polyfabrics, porcelain spot plates, TLC plates, corvettes, beakers, jars and the like may have been used to perform testing. All of these testing devices and methods may have been limited in the past as discussed above making them cumbersome and unwieldy to use and thereby limiting the flexibility necessary for quick, site selected and timely testing for detection of the presence of explosives or explosive residue.